Connectors and housing components used in under-the-hood applications in automobiles must always pass severe tests. To meet these demanding requirements, BASF has developed two new hydrolysis-resistant PBT compounds (Ultradur B4300G6 HR and Ultradur B4330G6 HR), each of which is available with 30 % glass fiber reinforcement.
Both of these new products have passed the requirements specified in USCar PF-1 Class III. Since hydrolysis resistance in electrical applications is not regulated in a standard manner, some manufacturers require in addition to the USCar-Test, which provides information on resistance under specific humidity and temperature conditions, additional tests. These include resistance to alkaline solutions under a bending stress as well as further tests involving storage/exposure to humidity.
Standard products from BASF have been compared to the new hydrolysis-resistant material grades using various test methods. Under a 2 % bending stress in alkaline solution, the materials were subjected to the bending stress test defined in DIN EN ISO 4599. Of the tensile bars made from the standard material, some broke after 2 h, while all failed after 24 h. The new, hydrolysis-stabilized PBT grades exhibit a relatively high NaOH resistance at room temperature. In contrast to the standard material, the first stress-induced cracks appear in these new products only after 24 h. The test results at a 2.78 % bending stress confirm the very good hydrolysis resistance of the new PBT grades also in comparison to competitive products. While the two test specimens made from competitive materials break 10 s at the latest after contact with the NaOH solution, the Ultradur B4330 G6 HR grade exhibits no cracks even after 52 h of contact.
After being stored at 85°C and 85% relative humidity as well as at 110°C and 100 % humidity, the new PBT grades exhibit very good hydrolysis-resistant behavior and lose no more than 20% of their initial material characteristics. After eight days of storage under these aggravated hydrolyzing conditions, the standard product is useless, since the mechanical properties drop by about 70 %. This new product line expands the field of application for PBT under extreme conditions. Components produced from the new material grades can better meet the increasingly demanding requirements of automakers than the standard products can.
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